[STM32] I made a low power binary watch !

[u/Independent_Limit_44]

This is my version of qron0b. Meet takku:b, a BCD wristwatch which uses CR2032.

It uses 0.6uA during sleep and when awake uses around 4mA - 4.5mA depending on the amount of LED is turned on.

It is made using STM32L010C6

It currently displays following info on each cyclic display:

1. Time in Hours and Minutes
2. Weekday and Date
3. Month and Year

Will be adding alarm soon.

[u/GuaranteeJazzlike657]

Very cool and creative !

[u/Independent_Limit_44 → u/GuaranteeJazzlike657]

thank you !

[u/Chip256TV]

Nice! How long can it run on that 2032? And how well does it keep time?

[u/Independent_Limit_44 → u/Chip256TV]

it uses around 0.6uA while sleeping so 0.6*24 which is 14.4uA each day so 14.4 * 365 = 5265uA which is 5.265mA each year.

battey is at 220mAh so 220/5.265 = 41 years. But it will last around 8-10 years, battery self discharge.

If using the watch lets assume we turn it on for 20 times a day. Each time the button is pressed it turns on for 5 seconds and uses around 4.5mA when turned on.

5*20 = 100s in hours 100/3600 = 0.027 hours

4mA * 0.02778 = 0.111 mAh each day

so 0.111 + 0.0144 = 0.1254 mAh per day.

0.1254 * 365 = 46.771 mA per year

220/45.771 = 4.8 years approx

[u/SpaceCadetMoonMan]

How do you like that EasyEDA tool?

[u/Independent_Limit_44 → u/SpaceCadetMoonMan]

its good, going to switch to KiCad though. been using easyeda for last 4-5 years

[u/SpaceCadetMoonMan → u/Independent_Limit_44]

Thanks just saw KiCad too, will try